Field of the Invention
The present invention relates to a heat exchanger that a plurality of heat transfer tubes are housed in a case and to a production method of the heat exchanger.
Description of the Related Art
The applicant of the present invention has proposed the heat exchanger disclosed in Patent Literature 1 as one example of such a heat exchanger.
The heat exchanger disclosed in Patent Literature 1 is bulged out of a part of the side wall of the case that a plurality of heat transfer tubes are housed inside and the bulging portion constitutes a header for entering water or delivering heated water. A practical means for utilizing the bulging portion as the header is an auxiliary member through which the ends of the heat transfer tubes are designed to penetrate. The auxiliary member is jointed in the bulging portion and separates the inside of the bulging portion from the inside of the case.
In such a configuration, the header is integrally provided with the side wall of the case, thereby being capable of reducing the number of members and downsizing the apparatus. The bulging portion bulges out of the case, thereby avoiding such a disadvantage that arrangement of the heat transfer tube is largely restricted because of a reduced space in the case; for example, unlike the heat exchanger disclosed in Patent Literature 2.
However, there is still a room for improvement in the conventional art as mentioned below.
The auxiliary member is required to be jointed in the bulging portion and the jointing portion is to be positioned in the case. Therefore, it is difficult to use welding as a jointing means of the jointing portion and brazing is required. However, brazing needs large equipment such as a vacuum furnace, thereby increasing the facility cost. As a result, the production cost of the heat exchanger also increases. In addition, when brazing is executed in the case, it is difficult to check whether brazing is appropriately done or not, thereby quality control becomes difficult.
Conventionally, some heat exchangers are capable of being manufactured by welding, unlike Patent Literature 1. However, such a heat exchanger comprises a number of members and has a complicated structure. Therefore, the production cost of such a heat exchanger becomes high.